Copolymers of ethylene with unsaturated esters and oil compositions containing said copolymers

ABSTRACT

Copolymers comprising within the range of 40 to 89 wt. percent ethylene, 10 to 40 wt. percent of vinyl ester of C2 to C4 monocarboxylic acid, and 1 to 30 wt. percent of unsaturated ester having a C10 to C22 alkyl group and having number average molecular weights within the range of 1,000 to 50,000, are useful in oil, e.g., as pour point depressants in distillate petroleum fuels and as dewaxing aids.

United States Patent Ilnyckyj [4 1 Feb. 15, 1972 [54] COPOLYMERS OFETI-IYLENE WITH UNSATURATED ESTERS AND OIL COMPOSITIONS CONTAINING SAIDCOPOLYMERS [72] Inventor: Stephan Ilnyckyj, Islington, Ontario, Canada I[73] Assignee: Esso Research and Engineering Company [22] Filed: Apr. 1,1968 211 App]. No.2 717,915

[52] US. Cl ..44/62, 44/70 [51] Int. Cl. ..Cl0l1/18 [58] Field of Search..44/62, 70; 260/8081 [56] References Cited UNITED STATES PATENTS3,467,597 9/1969 Tunkel ct a1 ..44/70 Primary Examiner-Daniel E. WymanAssistant ExaminerY. H. Smith Attorney-Pearlman and Schlager and FrankT. Johmann [5 7] ABSTRACT 3 Claims, No Drawings BACKGROUND OF THEINVENTION 1. Field of the Invention The present invention relates tocopolymers of ethylene with vinyl ester of C to C,, monocarboxylic acidand copolymerizable unsaturated esters having C to C alkyl groups, whichcopolymers are useful as pour point depressants in distillate petroleumfuels and as dewaxing aids.

2. Description of the Prior Art Copolymers of ethylene and vinyl estersof lower fatty acids, particularly vinyl acetate, are described in US.Pat. No. 3,048,479 as effective pour point depressants for middledistillate fuels. These prior pour point depressants, while veryeffective in treating the distillate oil to lower the pour point,frequently result in wax crystals having large particle sizes rangingfrom 1 millimeter up to an inch in their largest dimension. While thetreated distillate oil containing these large wax crystals exhibits apour point significantly under the original pour point of the untreatedoil, in many cases the large wax crystals will tend to plug filterequipment normally used on delivery trucks and fuel oil storage systems,when the oil is cooled below its cloud point, even though above its pourpoint. Thus, as the oil containing the pour point depressant is cooled,the cloud point (the point at which the oil becomes cloudy due tocrystallization of wax) will be reached at a temperature significantlyabove the pour point (the point at which the oil can no longerconveniently be poured). As a result, oils below their cloud point andabove their pour point will be pourable, but at the same time the waxcrystals that have formed, if too large, can result in plugging thefilters, that are used as protection against foreign matter, in thedispensing system.

SUMMARY OF THE INVENTION It has now been found that by copolymerizing asmall amount of copolymerizable unsaturated ester, having C to C alkylgroups, with ethylene and the lower vinyl esters, e.g., vinyl acetate,that the good pour point reduction of the ethylene-vinyl acetatecopolymer is still retained and smaller wax crystals are formed duringcooling of the treated oil. Specifically, the maximum size of the waxcrystals that are formed on cooling at rates encountered during coldweather are generally significantly reduced to a particle size in theorder of about 0.1 millimeter or less. As a result, even though thecloud point of the oil treated with this new polymer is substantiallythe same as the cloud point when the oil is treated with the oldcopolymer of ethylene and vinyl acetate, an important improvement infilterability is obtained in actual operating use. Thus, the new polymereliminates a problem of clogged filters associated with the conventionalpumps employed on oil delivery trucks, and also with the usual screensused in conjunction with the oil storage tanks to prevent the accidentalinclusion of foreign matter in the oil system. These screenstraditionally are in the order of 60 mesh or coarser and have a tendencyto clog if the wax crystal size is too large. Also, in many cases, thenew polymer is also found more effective in lowering the pour point ofthe oil than the old copolymers ofethylene and vinyl acetate.

These new polymers of the invention will comprise in the range of about40 to 89 wt. percent, preferably 50 to 80 wt. percent, of ethylene; to40 wt. percent, preferably to 35 wt. percent, of vinyl ester of a C to Cfatty acid; 1 to 30 wt. percent, preferably 3 to 25 wt. percent, ofunsaturated ester having C to C alkyl groups, the resulting polymerbeing mineral oil soluble and having a number average molecular weightin the range of about 1,000 to 50,000, preferably, about 1,500 to about5,000.

Examples of the vinyl ester of C to C fatty acids include vinyl acetate,vinyl n-propionate, vinyl n-butyrate, vinyl isopropionate, etc., and anymixtures thereof.

The unsaturated esters with the C to C alkyl groups include thosecopolymerizable mono-ethylenically unsaturated, monoesters of thegeneral formula:

wherein X is a hydrogen or a methyl group, and Y is a OOCR or COORwherein R is a C to C preferably a C to C straight chain or branchedchain, alkyl group.

Examples of the long chain unsaturated monoesters include the vinylesters of C to C monocarboxylic acid (i.e., where Y is OOCR) such asvinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinylarachidate, etc. Other examples of said monoesters are acrylic or methylacrylic acid esters (i.e., where X is COOR) such as lauryl acrylate,stearyl acrylate, palmityl alcohol ester of alpha-methyl-acrylic acid, COxo alcohol ester of methacrylic acid, etc.

A number of ways of carrying out the polymerization is possible to formthe polymers of the invention. In general, the techniques taught forethylene-vinyl ester polymerizations in US. Pat. Nos. 3,048,479,3,131,168, 3,093,623 'and 3,254,063 can be used. However, a particularlyuseful technique is as follows: Solvent and a portion of each of theunsaturated esters, e.g., 5 to 30 percent, preferably 10 to 20 percent,of the total amount of each unsaturated ester used in the batch, arecharged to a stainless steel pressure vessel which is equipped with astirrer. The temperature of the pressure vessel is then brought toreaction temperature and pressured to the desired pressure withethylene. Then a catalyst and additional amounts of each vinyl ester areadded to the vessel periodically or continuously during the reactiontime. Also during this reaction time, as ethylene is consumed in thepolymerization, additional ethylene is supplied through apressure-controlling regulator so as to maintain the desired reactionpressure fairly constant at all times. Following the completion of thereaction, the liquid phase of the pressure vessel is distilled to removethe solvent and other volatile constituents of the reacted mixture,leaving the polymer as residue. In general, based upon parts by weightof polymer to be produced, then about 100 to 600 parts by weight ofsolvent, and about one to 10 parts by weight of catalyst, will be used.

The catalyst, or promoter, will generally be of the free radical type,including organic peroxide types such as benzoyl peroxide, ditertiarybutyl peroxide, dicumyl peroxide, tertiary butyl perbenzoate, lauroylperoxide, t-butyl hydroperoxide, and also such nonperoxy compounds asazo-bis-isobutyronitrile, and the like.

The solvent can be any nonreactive organic solvent for furnishing aliquid phase reaction, preferably hydrocarbon solvent such as benzene,or hexane, etc.

Temperatures and pressures employed may vary widely. For example,depending partly on the decomposition temperature of the catalyst, thetemperature may range from 100 F. to 450 F. with pressures of 500 to30,000 p.s.i.g. However, usually the temperature will range betweenabout F. and about 350 F., and relatively moderate pressures of 700 toabout 3,000 p.s.i.g. will be used. It is only important that asuperatmospheric pressure be employed, which is at least sufficient tomaintain a liquid phase medium under the reaction conditions, and issufficient to maintain the desired concentration of ethylene in solutionin the solvent. In general, this pressure is attained by maintaining acontinuous pressure on the reaction chamber through controlling theinlet feed of ethylene.

The time of reaction will depend upon, and is interrelated to, thetemperature of the reaction, the choice of catalyst, and the pressureemployed. In general, however, 1 to 10 hours will complete the reaction.

The polymers of the invention will generally be added to hydrocarbonoils in amounts of 0.001 to 2 wt. percent, generally 0.005 to about 0.5wt. percent, said wt. percent being based upon the weight of the oil tobe treated.

The hydrocarbon oils, which are treated for pour depression with thepolymers of this invention, include cracked and virgin distillate oilsboiling in the range of 250 to 750 F., such as kerosene, heating oil,diesel fuel oil, etc. Also, fuel oil blends comprising a major amount ofdistillate oil boiling in the aforesaid 250 to 750 F. range and a minoramount of higher boiling residual oil can also be treated for pourdepression. In addition, the polymers of the invention can be used as adewaxing aid during dewaxing of light distillate lube oil stocks boilingin the 600-1,000 F. range in the manner similar to that taught in U.S.Pat. No. 3,262,873.

The polymers of the invention may be used alone as the sole oiladditive, or in combination with other oil additives such as other pourdepressants or dewaxing aids; corrosion inhibitors, such as sodiumnitrite and dicyclohexyl ammonium nitrite; antioxidants such asoctadecylamine; sludge inhibitors; etc.

The invention will be further understood by reference to the followingexamples which include a preferred embodiment of the invention.

EXAMPLE I A l-gallon stirred autoclave was first flushed with nitrogenand then ethylene. The autoclave charged with 1,145 ml. of benzene assolvent, 50 ml. of vinyl acetate, and ml. of vinyl laurate was thenheated to 335 F. and ethylene pressured into the autoclave until thepressure was raised to 1,250 p.s.i.g. Then ditertiary butyl peroxide ascatalyst and additional vinyl acetate and vinyl laurate werecontinuously injected into the autoclave at an even rate. A total of 9ml. of the peroxide was injected over 1% hours, while 300 ml. of vinylacetate and 80 ml. of vinyl laurate were injected into the reactor overa period of 1% hours from the start of the injection. At the end of 1%hours, the temperature of the reactor contents was lowered to 200 F. andthe product was discharged from the autoclave. The product was thenstripped of the solvent and unreacted monomers by distillation underslightly reduced pressure. Next, excess vinyl laurate was removedoverhead by high vacuum distillation, that is, under a pressure of about2 mm. Hg. The final product consisted of 441 grams of terpolymer.

EXAMPLE II A polymer was prepared under the identical conditions ofExample 1, except the quantities of vinyl esters had been changed asfollows: The initial charges of vinyl acetate and vinyl laurate amountedto 40 ml. and 35 ml., respectively, and 250 ml. of vinyl acetate and 230ml. of vinyl laurate were each injected over a 1% hour period. 727 gramsof the terpolymer were obtained.

COMPARISON A To show the effect of excluding the higher vinyl ester, acopolymerization was carried out under conditions similar to those ofExample 1, except vinyl laurate was excluded, the initial charge ofvinyl acetate amounted to 55 ml., and 300 ml. of additional vinylacetate was injected over 1% hours. The copolymer yield amounted to 550grams.

The above polymers of Examples 1, II and Comparison A, since they wereprepared under similar conditions, would have comparable molecularweights, which prior experience indicates would be about 2,000 numberaverage molecular weight.

The polymers prepared above were tested for pour depression in a testfuel oil which was a gas oil distillate fuel oil (50 percent virgin 50percent cracked) having a pour point of +25 F. and an ASTM final boilingpoint of 660 F. The compositions of the polymers, the concentrationsused in the test fuel oil, and the pour points (ASTM D97) obtained, aresummarized in the following table:

TABLE Composition of Polymer, wl. Example Example Comparison I II AEthylene 65 60 70 Vinyl acetate 28 20 30 Vinyl laurate 7 20 0 Pour Pointat 0.0l0 wt. polymer 0 F 5 F. 5 F. Pour Point at 0.015 wt. k polymer 25F. 20 F. 15 F. Pour Point at v 0.018 wt. polymer 60 F. -35 F. 25 F.

As seen by the above table, the copolymers of Examples l and II atconcentrations of 0.015 wt. percent (based on the weight of the testoil) and above, were more effective in reducing the pour point of theoil than the Comparison A polymer which did not contain the higher vinylester.

The superiority of the polymers of the invention are furtherdemonstrated by a filterability test. This test was carried out using astraight run distillate paraffin base fuel oil having a boiling range of336 to 646 F. according to ASTM D-86; an ASTM cloud point of 14 F. andan ASTM pour point of 5 F. The Filterability Test measures the abilityof an oil, when cloudy, to pass through filters encountered in oildistribution systems. This test is carried out in a cylindrical jarconsisting of two chambers separated by a partition. Each chamber has acapacity of 200 ml. The partition is provided with an opening having anarea of 0.2 square inches. A U.S. 40-mesh screen is inserted into theopening which is then plugged with a stopper. 200 ml. of oil are pouredinto the upper chamber and the tester containing the oil is then chilledat a rate of 1 F. per hour to a temperature 5 F. below the ASTM cloudpoint of the oil. At this point, the stopper is pulled out from theopening allowing the cloudy oil to flow into the lower chamber. In orderto be considered of satisfactory quality, at least 90 percent of thesample has to pass into the lower chamber in no more than 25 seconds.0.05 wt. percent of the polymer product of Example I in the test oilreduced the pour point a total of 55 F. and gave a percent pass in thefilterability test at 7 F. In comparison, 0.05 wt. percent ofacommercial ethylene vinyl acetate pour point depressant consisting ofabout 70 wt. percent ethylene and 30 wt. percent vinyl acetate andhaving a number average molecular weight of about 2,000, gave a pourdepression of 45 F. but only a 25 percent passage in the filterabilitytest. In addition, examination of the wax crystals formed when the oilcontaining the 0.05 wt. percent of the polymer of Example I was cooledat the rate of 1 F. down to the pour point, showed that the wax crystalsmea sured approximately 0.1 mm. in their longest dimension, while thewax crystals formed using an equal amount of the aforesaid commercialpour depressant measured approximately about 1 mm. across their longestdimension.

As a further illustration of the invention a polymer is prepared in thegeneral manner of Example I, but using stearyl acrylate in place of thevinyl laurate, and 0.1 wt. percent of the resulting terpolymer can beadded to the oil used in the aforementioned table.

What is claimed is:

l. A petroleum distillate oil boiling in the range of about 250-1,000F., containing about 0.001 to about 2 wt. percent of a polymercomprising about 40 to 89 wt. percent ethylene, about 10 to 40 wt.percent vinyl ester ofC to C monocarboxylic acid, about 1 to 30 wt.percent of unsaturated ester represented by the formula:

wherein X is selected from the group consisting of hydrogen and methylgroups, and Y is the OOCR radical in which R is a C to C alkyl group,said polymer having a number average molecular weight of about 1,000 to50,000.

2. A petroleum distillate oil boiling in the range of about 250-750 F.,containing about 0.005 to 0.5 wt. percent of a polymer comprising about40-89 wt. percent ethylene, about -40 wt. percent vinyl acetate andabout 1-30 wt. percent of unsaturated ester represented by the formula:

2. A petroleum distillate oil boiling in the range of about 250*-750*F., containing about 0.005 to 0.5 wt. percent of a polymer comprisingabout 40-89 wt. percent ethylene, about 10-40 wt. percent vinyl acetateand about 1-30 wt. percent of unsaturated ester represented by theformula: wherein X is selected from the group consisting of hydrogen andmethyl and Y is OOCR derived from lauric acid, said polymer having anumber average molecular weight of about 1,000-50,000.
 3. A petroleumdistillate oil boiling in the range of about 250*-1,000* F. andcontaining about 0.001 to 2 wt. percent of a terpolymer consistingessentially of about 50 to 80 wt. percent ethylene, about 15 to 35 wt.percent vinyl acetate, and about 3 to 25 wt. percent vinyl laurate andhaving a number average molecular weight of about 1,500 to 5,000.